1. Technical Field
The present invention relates to a vehicle power assist steering system. In particular, the present invention relates to an electric power assist steering system that includes an electric assist motor and a circuit board, or electronic control module, that is mounted in a housing together with the motor.
2. Description of the Prior Art
A known type of vehicle power assist steering system includes a ball nut for transmitting force between a steering member and an electric assist motor. The steering system also includes an electronic control unit, or ECU, for controlling operation of the electric motor and for providing current to the motor. Upon actuation of the electric motor, the ball nut is driven to rotate relative to the steering member. The rotational force of the ball nut is transmitted to the steering member to drive the steering member axially. Axial movement of the steering member effects turning movement of the steerable wheels of the vehicle.
U.S. Pat. No. 5,573,079 shows an electrically operated steering apparatus including a motor driver circuit disposed in a cylindrical housing for energizing an electric motor.
U.S. Pat. No. 5,265,322 shows an electric module assembly and method of forming same including a circuit board that is bent to have a three-dimensional configuration.
The present invention is a steering assembly for turning steerable wheels of a vehicle in response to rotation of a steering wheel of the vehicle. The steering assembly includes a pinion, and a steering member that is movable axially to effect turning movement of the steerable wheels of the vehicle. The steering member has a rack portion in engagement with the pinion and an externally threaded screw portion. The steering assembly includes an electric motor comprising a rotor and a stator, the stator when energized effecting rotation of the rotor. The screw thread portion of the steering member extends axially through the electric motor. A ball nut rotatable with the rotor is associated with the screw thread portion of the steering member for effecting axial movement of the steering member in response to rotation of the rotor thereby to turn the steerable wheels of the vehicle. The steering assembly further includes an electronic control unit for helping to control operation of the electric motor. The electronic control unit includes a circuit board and a plurality of electronic components mounted on the circuit board. The circuit board has a non-planar configuration and at least partially encircles a portion of the steering member at a location spaced axially from the electric motor.